Dressing with asymmetric absorbent core for negative pressure wound therapy

ABSTRACT

Systems, methods, and apparatuses for treating a tissue site with reduced pressure are described. The system includes a manifold configured to be placed adjacent the tissue site, and a sealing member configured to be placed over the tissue site and the manifold. The system also includes a reduced-pressure source fluidly coupled to the manifold through the sealing member. The system further includes a pouch having an upstream layer having a first thickness, a downstream layer having a second thickness, and an absorbent member enclosed between the upstream layer and the downstream layer. The second thickness is greater than the first thickness. The upstream layer may have a hydrophilic side adjacent the absorbent member, and the downstream layer may have a hydrophobic side adjacent the absorbent member.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/150,262, filed Jan. 8, 2014, which claims the benefit, under 35 USC119(e), of the filing of U.S. Provisional Patent Application No.61/753,368, entitled “Dressing with Asymmetric Absorbent Core forNegative Pressure Wound Therapy,” filed Jan. 16, 2013, which isincorporated herein by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates generally to medical treatment systemsfor treating tissue sites and processing fluids. More particularly, butnot by way of limitation, the present disclosure relates to a dressinghaving an asymmetric absorbent core for reduced-pressure wound therapy.

BACKGROUND

Clinical studies and practice have shown that reducing pressure inproximity to a tissue site can augment and accelerate growth of newtissue at the tissue site. The applications of this phenomenon arenumerous, but is has proven particularly advantageous for treatingwounds. Regardless of the etiology of a wound, whether trauma, surgery,or another cause, proper care of the wound is important to the outcome.Treatment of wounds with reduced pressure may be commonly referred to as“reduced-pressure wound therapy,” but is also known by other names,including “negative-pressure therapy,” “negative pressure woundtherapy,” and “vacuum therapy,” for example. Reduced-pressure therapymay provide a number of benefits, including migration of epithelial andsubcutaneous tissues, improved blood flow, and micro-deformation oftissue at a wound site. Together, these benefits can increasedevelopment of granulation tissue and reduce healing times.

While the clinical benefits of reduced-pressure therapy are widelyknown, the cost and complexity of reduced-pressure therapy can be alimiting factor in its application, and the development and operation ofreduced-pressure systems, components, and processes continues to presentsignificant challenges to manufacturers, healthcare providers, andpatients. In particular, reduced-pressure dressings that include anabsorbent member positioned proximate a tissue site may experienceabsorbent material loss or inefficient absorption that negativelyimpacts the ability of a reduced-pressure system to providereduced-pressure therapy to a tissue site.

SUMMARY

According to an illustrative embodiment, a system for collecting fluidfrom a tissue site is described. The system may include a manifoldadapted to be placed adjacent the tissue site, a sealing member adaptedto be placed over the tissue site and a reduced-pressure source adaptedto be fluidly coupled to the manifold through the sealing member. Thesystem further may include a pouch. The pouch may include an upstreamlayer having a first thickness, a hydrophilic side, and a hydrophobicside, and a downstream layer having a second thickness, a hydrophilicside, and a hydrophobic side. The apparatus also may include anabsorbent member enclosed between the upstream layer and the downstreamlayer. The hydrophilic side of the upstream layer may be positionedadjacent the absorbent member so that the hydrophobic side of theupstream layer forms a portion of an exterior of the apparatus. Thehydrophobic side of the downstream layer may be positioned adjacent theabsorbent member so that the hydrophilic side of the downstream layerforms another portion of the exterior of the apparatus. The secondthickness may be greater than the first thickness.

According to another illustrative embodiment, a system for treating atissue site with reduced pressure is described. The system may include amanifold adapted to be placed adjacent the tissue site, a sealing memberadapted to be placed over the tissue site and the manifold to provide asubstantially air-tight seal at the tissue site, and a reduced-pressuresource adapted to be fluidly coupled to the manifold through the sealingmember. The system further may include a pouch. The pouch may include anupstream layer having a hydrophilic side and a hydrophobic side, adownstream layer having a hydrophilic side and a hydrophobic side, andan absorbent member enclosed between the upstream layer and thedownstream layer. The hydrophilic side of the upstream layer may bepositioned adjacent the absorbent member, and the hydrophobic side ofthe downstream layer may be positioned adjacent the absorbent member.The pouch may be adapted to be positioned between the manifold and thesealing member.

According to yet another illustrative embodiment, an apparatus forcollecting fluid from a tissue site is described. The apparatus mayinclude an upstream layer having a hydrophilic side and a hydrophobicside, and a downstream layer having a hydrophilic side and a hydrophobicside. The apparatus also may include an absorbent member enclosedbetween the upstream layer and the downstream layer. The hydrophilicside of the upstream layer may be positioned adjacent the absorbentmember so that the hydrophobic side of the upstream layer forms aportion of an exterior of the apparatus. The hydrophobic side of thedownstream layer may be positioned adjacent the absorbent member so thatthe hydrophilic side of the downstream layer forms another portion ofthe exterior of the apparatus.

According to still another illustrative embodiment, a system fortreating a tissue site with reduced pressure is described. The systemmay include a manifold adapted to be placed adjacent the tissue site, asealing member adapted to be placed over the tissue site and themanifold to provide a substantially air-tight seal at the tissue site,and a reduced-pressure source adapted to be fluidly coupled to themanifold through the sealing member. The system further may include apouch. The pouch may have an upstream layer having a first thickness, adownstream layer having a second thickness, and an absorbent memberenclosed between the upstream layer and the downstream layer. The secondthickness may be greater than the first thickness, and the pouch may beadapted to be positioned between the manifold and the sealing member.

According to still another illustrative embodiment, an apparatus forcollecting fluid from a tissue site is described. The apparatus mayinclude a pouch. The pouch may have an upstream layer having a firstthickness, a downstream layer having a second thickness, and anabsorbent member enclosed between the upstream layer and the downstreamlayer. The second thickness may be greater than the first thickness, andthe pouch may be adapted to be positioned between the manifold and thesealing member.

According to yet another illustrative embodiment, a method for treatinga tissue site is described. The method positions a manifold adjacent thetissue site and provides a pouch. The pouch may include an upstreamlayer having a hydrophilic side and a hydrophobic side, a downstreamlayer having a hydrophilic side and a hydrophobic side, and an absorbentmember enclosed between the upstream layer and the downstream layer. Thehydrophilic side of the upstream layer may be positioned adjacent theabsorbent member so that the hydrophobic side of the upstream layerforms a portion of an exterior of the apparatus. The hydrophobic side ofthe downstream layer may be positioned adjacent the absorbent member sothat the hydrophilic side of the downstream layer forms another portionof the exterior of the apparatus. The method may position the pouchadjacent the manifold and the tissue site so that the upstream layer isadjacent the manifold. The pouch may include an upstream layer having afirst thickness, a downstream layer having a second thickness greaterthan the first thickness, and an absorbent member having absorbentmaterial disposed between the upstream layer and the downstream layer sothat the upstream layer and the downstream layer enclose the absorbentmember. The method may position a sealing member over the manifold andthe pouch to provide a substantially air-tight seal and fluidly couplesa reduced-pressure source to the manifold to provide reduced pressure tothe tissue site. The method may distribute reduced pressure to themanifold through the pouch and distributes fluid from the tissue site toan absorbent member in the pouch for storage therein.

According to another illustrative embodiment, a method for manufacturinga fluid storage canister is described. The method provides a first layerhaving a first thickness, a hydrophilic side, and a hydrophobic side.The method positions an absorbent member adjacent the hydrophilic sideof the first layer. The method also provides a second layer have asecond thickness greater than the first thickness, a hydrophilic sideand a hydrophobic side. The method positions the hydrophilic side of thesecond layer adjacent the absorbent member. The method couplesperipheral portions of the first layer and the second layer to eachother to enclose the absorbent member.

Other aspects, features, and advantages of the illustrative embodimentswill become apparent with reference to the drawings and detaileddescription that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is sectional view illustrating a reduced-pressure therapy systemin accordance with an exemplary embodiment;

FIG. 2 is a sectional view illustrating a pouch of the reduced-pressuretherapy system of FIG. 1; and

FIG. 3 is an exploded sectional view of the pouch of FIG. 2.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

New and useful systems, methods, and apparatuses for fluid storage in areduced-pressure therapy environment are set forth in the appendedclaims. Objectives, advantages, and a preferred mode of making and usingthe systems, methods, and apparatuses may be understood best byreference to the following detailed description in conjunction with theaccompanying drawings. The description provides information that enablesa person skilled in the art to make and use the claimed subject matter,but may omit certain details already well-known in the art. Moreover,descriptions of various alternatives using terms such as “or” do notnecessarily require mutual exclusivity unless clearly required by thecontext. The claimed subject matter may also encompass alternativeexemplary embodiments, variations, and equivalents not specificallydescribed in detail. The following detailed description should thereforebe taken as illustrative and not limiting.

The exemplary embodiments may also be described herein in the context ofreduced-pressure therapy applications, but many of the features andadvantages are readily applicable to other environments and industries.Spatial relationships between various elements or to the spatialorientation of various elements may be described as depicted in theattached drawings. In general, such relationships or orientations assumea frame of reference consistent with or relative to a patient in aposition to receive reduced-pressure therapy. However, as should berecognized by those skilled in the art, this frame of reference ismerely a descriptive expedient rather than a strict prescription.

FIG. 1 is a sectional view of an exemplary embodiment illustrating atherapy system 100 for supplying reduced pressure to a tissue site 106.The therapy system 100 may include a dressing 102 in fluid communicationwith the tissue site 106, a reduced-pressure source 104 for providingreduced pressure to a tube 120 that may be fluidly coupled to thereduced-pressure source 104, and a connector 122 that may fluidly couplethe tube 120 to the dressing 102.

The term “tissue site” in this context broadly refers to a wound ordefect located on or within tissue, including but not limited to, bonetissue, adipose tissue, muscle tissue, neural tissue, dermal tissue,vascular tissue, connective tissue, cartilage, tendons, or ligaments. Atissue site may include chronic, acute, traumatic, subacute, anddehisced wounds, partial-thickness burns, ulcers (such as diabetic,pressure, or venous insufficiency ulcers), flaps, and grafts, forexample. The term “tissue site” may also refer to areas of any tissuethat are not necessarily wounded or defective, but are instead areas inwhich it may be desirable to add or promote the growth of additionaltissue. For example, reduced pressure may be used in certain tissueareas to grow additional tissue that may be harvested and transplantedto another tissue location.

A reduced-pressure source, such as the reduced-pressure source 104, maybe a reservoir of air at a reduced pressure, or may be a manually orelectrically-powered device that can reduce the pressure in a sealedvolume, such as a vacuum pump, a suction pump, a wall suction portavailable at many healthcare facilities, or a micro-pump, for example.The reduced-pressure source may be housed within or used in conjunctionwith other components, such as sensors, processing units, alarmindicators, memory, databases, software, display devices, or userinterfaces that further facilitate reduced-pressure therapy. While theamount and nature of reduced pressure applied to a tissue site may varyaccording to therapeutic requirements, the pressure typically rangesbetween −5 mm Hg (−667 Pa) and −500 mm Hg (−66.7 kPa). Commontherapeutic ranges are between −75 mm Hg (−9.9 kPa) and −300 mm Hg(−39.9 kPa).

The fluid mechanics of using a reduced-pressure source to reducepressure in another component or location, such as within a sealedtherapeutic environment, can be mathematically complex. However, thebasic principles of fluid mechanics applicable to reduced-pressuretherapy are generally well-known to those skilled in the art, and theprocess of reducing pressure may be described illustratively herein as“delivering,” “distributing,” or “generating” reduced pressure, forexample.

In general, exudates and other fluids flow toward lower pressure along afluid path. This orientation may be generally presumed for purposes ofdescribing various features and components of reduced-pressure therapysystems herein. Thus, the term “downstream” typically implies somethingin a fluid path relatively closer to a reduced-pressure source, andconversely, the term “upstream” implies something relatively furtheraway from a reduced-pressure source. Similarly, it may be convenient todescribe certain features in terms of fluid “inlet” or “outlet” in sucha frame of reference. However, the fluid path may also be reversed insome applications (such as by substituting a positive-pressure sourcefor a reduced-pressure source) and this descriptive convention shouldnot be construed as a limiting convention.

“Reduced pressure” generally refers to a pressure less than a localambient pressure, such as the ambient pressure in a local environmentexternal to a sealed therapeutic environment. In many cases, the localambient pressure may also be the atmospheric pressure at which a patientis located. Alternatively, the pressure may be less than a hydrostaticpressure associated with tissue at the tissue site. Unless otherwiseindicated, values of pressure stated herein are gauge pressures.Similarly, references to increases in reduced pressure typically referto a decrease in absolute pressure, while decreases in reduced pressuretypically refer to an increase in absolute pressure.

The components of the therapy system 100 may be coupled directly orindirectly. Components may be fluidly coupled to each other to provide apath for transferring fluids (for example, liquid and/or gas) betweenthe components. In some exemplary embodiments, components may be fluidlycoupled with a conduit, such as the tube 120, for example. A “tube,” asused herein, broadly refers to a tube, pipe, hose, conduit, or otherstructure with one or more lumina adapted to convey fluids between twoends. Typically, a tube may be an elongated, cylindrical structure withsome flexibility, but the geometry and rigidity may vary. In someexemplary embodiments, components may additionally or alternatively becoupled by virtue of physical proximity, being integral to a singlestructure, or being formed from the same piece of material. Coupling mayalso include mechanical, thermal, electrical, or chemical coupling (suchas a chemical bond) in some contexts.

The reduced pressure developed by the reduced-pressure source 104 may bedelivered through the tube 120 to the connector 122. The connector 122may be a device configured to fluidly couple the reduced-pressure source104 to the dressing 102. In some exemplary embodiments, the connector122 may include a flange portion 123 that may couple to the dressing 102and a port portion that may fluidly couple to the tube 120. The portportion may be fluidly sealed to the flange portion 123 and may providefluid communication through the flange portion 123. In some embodiments,the connector 122 may prevent fluid communication between a sealedtherapeutic environment formed by the dressing 102 and the ambientenvironment. The connector 122 may allow fluid communication through thedressing 102 between the tissue site 106 and the tube 120. The connector122 may also include a primary filter 121 disposed within a fluidchannel of the connector 122. The primary filter 121 may be ahydrophobic material substantially filling the fluid channel through theconnector 122 and adapted to limit passage of liquids through theconnector 122 into the tube 120. In some embodiments, the connector 122may be a T.R.A.C.® Pad or Sensa T.R.A.C.® Pad available from KineticConcepts, Inc. (KCI) of San Antonio, Tex. In other exemplaryembodiments, the connector 122 may be a conduit inserted into thedressing 102.

The dressing 102 may include a manifold 110 adapted to be in fluidcommunication with the tissue site 106, a pouch 112 adapted to be influid communication between the manifold 110 and the connector 122, anda drape 108 covering both the manifold 110 and the pouch 112 at thetissue site 106. The manifold 110 may be placed within, over, on, orotherwise proximate a tissue site, for example, the tissue site 106. Thepouch 112 may be placed adjacent the manifold 110, and the drape 108 maybe placed over the manifold 110 and sealed to tissue proximate thetissue site 106. The tissue proximate the tissue site 106 may often beundamaged epidermis peripheral to the tissue site 106. Thus, thedressing 102 can provide the sealed therapeutic environment proximatethe tissue site 106, substantially isolating the tissue site 106 fromthe external environment. The reduced-pressure source 104 can reduce thepressure in the sealed therapeutic environment. Reduced pressure applieduniformly through the manifold 110 in the sealed therapeutic environmentcan induce macrostrain and microstrain in the tissue site 106, as wellas remove exudates and other fluids from the tissue site 106, which canbe collected in the pouch 112 and disposed of properly.

In some embodiments, the manifold 110 contacts the tissue site 106. Themanifold may be partially or fully in contact with the tissue site 106.If the tissue site 106 extends into tissue from a tissue surface, forexample, the manifold 110 may partially or completely fill the tissuesite 106. In other exemplary embodiments, the manifold 110 may be placedover the tissue site 106. The manifold 110 may take many forms, and mayhave many sizes, shapes, or thicknesses depending on a variety offactors, such as the type of treatment being implemented or the natureand size of the tissue site 106. For example, the size and shape of themanifold 110 may be adapted to the contours of deep and irregular shapedtissue sites.

The manifold 110 may be a substance or structure adapted to distributereduced pressure to a tissue site, remove fluids from a tissue site, ordistribute reduced pressure to and remove fluids from a tissue site. Insome exemplary embodiments, a manifold may also facilitate deliveringfluids to a tissue site, for example, if the fluid path is reversed or asecondary fluid path is provided. A manifold may include flow channelsor pathways that distribute fluids provided to and removed from a tissuesite around the manifold. In one exemplary embodiment, the flow channelsor pathways may be interconnected to improve distribution of fluidsprovided to or removed from a tissue site. For example, cellular foam,open-cell foam, porous tissue collections, and other porous material,such as gauze or felted mat, generally include structural elementsarranged to form flow channels. Liquids, gels, and other foams may alsoinclude or be cured to include flow channels.

In one exemplary embodiment, the manifold 110 may be a porous foammaterial having interconnected cells or pores adapted to uniformly (orquasi-uniformly) distribute reduced pressure to the tissue site 106. Thefoam material may be either hydrophobic or hydrophilic. In onenon-limiting example, the manifold 110 can be an open-cell, reticulatedpolyurethane foam such as GranuFoam® dressing available from KineticConcepts, Inc. of San Antonio, Tex.

In an example in which the manifold 110 may be made from a hydrophilicmaterial, the manifold 110 may also wick fluid away from the tissue site106, while continuing to distribute reduced pressure to the tissue site106. The wicking properties of the manifold 110 may draw fluid away fromthe tissue site 106 by capillary flow or other wicking mechanisms. Anexample of a hydrophilic foam is a polyvinyl alcohol, open-cell foamsuch as V.A.C. WhiteFoam® dressing available from Kinetic Concepts, Inc.of San Antonio, Tex. Other hydrophilic foams may include those made frompolyether. Other foams that may exhibit hydrophilic characteristicsinclude hydrophobic foams that have been treated or coated to providehydrophilicity.

The manifold 110 may further promote granulation at the tissue site 106if pressure within the sealed therapeutic environment is reduced. Forexample, any or all of the surfaces of the manifold 110 may have anuneven, coarse, or jagged profile that can induce microstrains andstresses at the tissue site 106 if reduced pressure is applied throughthe manifold 110 to the tissue site 106.

In one exemplary embodiment, the manifold 110 may be constructed frombioresorable materials. Suitable bioresorbable materials may include,without limitation, a polymeric blend of polylactic acid (PLA) andpolyglycolic acid (PGA). The polymeric blend may also include, withoutlimitation, polycarbonates, polyfumarates, and capralactones. Themanifold 110 may further serve as a scaffold for new cell-growth, or ascaffold material may be used in conjunction with the manifold 110 topromote cell-growth. A scaffold is generally a substance or structureused to enhance or promote the growth of cells or formation of tissue,such as a three-dimensional porous structure that provides a templatefor cell growth. Illustrative examples of scaffold materials includecalcium phosphate, collagen, PLA/PGA, coral hydroxy apatites,carbonates, or processed allograft materials.

The drape 108 may include a sealing member. A sealing member may beconstructed from a material that can provide a fluid seal between twocomponents or two environments, such as between the sealed therapeuticenvironment and a local ambient environment. A sealing member may be,for example, an impermeable or semi-permeable, elastomeric material thatcan provide a seal adequate to maintain a reduced pressure at a tissuesite for a given reduced-pressure source. For semi-permeable materials,the permeability generally should be low enough that a desired reducedpressure may be maintained. The drape 108 may further include anattachment device that may be used to attach the sealing member to anattachment surface, such as undamaged epidermis, a gasket, or anothersealing member. The attachment device may take many forms. For example,an attachment device may be a medically acceptable, pressure-sensitiveadhesive that extends about a periphery of, a portion of, or an entiretyof the sealing member. Other exemplary embodiments of an attachmentdevice may include a double-sided tape, paste, hydrocolloid, hydrogel,silicone gel, organogel, or an acrylic adhesive.

Referring more specifically to FIG. 2, the pouch 112 may include anabsorbent member 124, a first outer layer, such as an upstream layer126, and a second outer layer, such as a downstream layer 128. Theupstream layer 126 and the downstream layer 128 envelop or enclose theabsorbent member 124, which absorbs bodily fluids drawn by the reducedpressure through the upstream layer 126.

The absorbent member 124 may be formed of or include an absorbentmaterial. The absorbent material functions to hold, stabilize, and/orsolidify fluids that may be collected from the tissue site 106. Theabsorbent material may be of the type referred to as “hydrogels,”“super-absorbents,” or “hydrocolloids.” If disposed within the dressing102, the absorbent material may be formed into fibers or spheres tomanifold reduced pressure until the absorbent member 124 becomessaturated. Spaces or voids between the fibers or spheres may allow areduced pressure that is supplied to the dressing 102 to be transferredwithin and through the absorbent member 124 to the manifold 110 and thetissue site 106. In some exemplary embodiments, the absorbent materialmay be Texsus FP2325 having a material density of 800 grams per squaremeter (gsm). In other exemplary embodiments, the absorbent material maybe BASF 402C, Technical Absorbents 2317 available from TechnicalAbsorbents (www.techabsorbents.com), sodium polyacrylate superabsorbers, cellulosics (carboxy methyl cellulose and salts such assodium CMC), or alginates.

In some exemplary embodiments, the absorbent material may be formed ofgranular absorbent components that may be scatter coated onto a papersubstrate. Scatter coating involves spreading a granular absorbentpowder uniformly onto a textile substrate, such as paper. The substrate,having the granular absorbent powder disposed thereon, may be passedthrough an oven to cure the powder and cause the powder to adhere to thepaper substrate. The cured granular absorbent powder and substrate maybe passed through a calender machine to provide a smooth uniform surfaceto the absorbent material. The absorbent materials that may be formedusing a scatter coating process experience partial absorbent materialloss during handling. The absorbent material loss may occur whilepositioning the absorbent material proximate the tissue site, whiletransporting the absorbent material from the manufacturing facility tothe facility of use, or during the process of manufacturing a pouchformed solely of absorbent material.

In some exemplary embodiments, the upstream layer 126 and the downstreamlayer 128 have perimeter dimensions that may be larger than theperimeter dimensions of the absorbent member 124 so that, if theabsorbent member 124 is positioned between the upstream layer 126 andthe downstream layer 128 and the center portions of the absorbent member124, the upstream layer 126, and the downstream layer 128 are aligned,the upstream layer 126 and the downstream layer 128 may extend beyondthe perimeter of the absorbent member 124. In some exemplaryembodiments, the upstream layer 126 and the downstream layer 128surround the absorbent member 124. Peripheral portions of the upstreamlayer 126 and the downstream layer 128 may be coupled so that theupstream layer 126 and the downstream layer 128 enclose the absorbentmember 124. The upstream layer 126 and the downstream layer 128 may becoupled by high frequency welding, ultrasonic welding, heat welding, orimpulse welding, for example. In other exemplary embodiments, theupstream layer 126 and the downstream layer 128 may be coupled bybonding or folding, for example.

Referring more specifically to FIG. 2 and FIG. 3, the upstream layer 126may have a first side, such as a hydrophobic side 130, and a secondside, such as a hydrophilic side 132. The hydrophilic side 132 may bepositioned adjacent the absorbent member 124 such that the hydrophobicside 130 of the upstream layer 126 is also an upstream side of the pouch112. The upstream layer 126 may be formed of non-woven material having athickness 138. In some exemplary embodiments, the upstream layer 126 mayhave a polyester fibrous porous structure. The upstream layer 126 may beporous, but preferably not be perforated. The upstream layer 126 mayhave a material density of about 80 gsm. In other exemplary embodiments,the material density may be lower or greater depending on the particularapplication of the pouch 112. The upstream layer 126 may be formed ofLibeltex TDL2, for example.

The hydrophobic side 130 may be configured to distribute bodily fluidsfrom the manifold 110 across the upstream surface area of the pouch 112.The hydrophobic side 130 may also be referred to as a wicking side,wicking surface, distribution surface, distribution side, or fluiddistribution surface. The hydrophobic side 130 may be a smoothdistribution surface configured to move fluid through the upstream layer126 along a grain of the upstream layer 126, distributing fluidthroughout the upstream layer 126. The hydrophilic side 132 may beconfigured to acquire bodily fluid from the hydrophobic side 130 to aidin bodily fluid movement into the absorbent member 124. The hydrophilicside 132 may also be referred to as a fluid acquisition surface, fluidacquisition side, hydrophilic acquisition surface, or hydrophilicacquisition side. The hydrophilic side 132 may be a fibrous surface andbe configured to draw fluid into the upstream layer 126. Whileillustrated in FIG. 3 as separate components, the hydrophilic side 132and the hydrophobic side 130 of the upstream layer 126 may be oppositesides of the upstream layer 126 and are shown as separate components toaid in explanation.

The downstream layer 128 may have a first side, such as a hydrophobicside 134, and a second side, such as a hydrophilic side 136. Thehydrophobic side 134 may be positioned adjacent the absorbent member 124so that the hydrophilic side 136 of the downstream layer 128 is also adownstream side of the pouch 112. The downstream layer 128 may be formedof a non-woven material having a thickness 140. In some exemplaryembodiments, the downstream layer 128 may have a polyester fibrousporous structure. The downstream layer 128 may be porous, but preferablynot be perforated. The downstream layer 128 may have a material densityof about 150 gsm. In other exemplary embodiments, the material densitymay be lower or greater depending on the particular application of thepouch 112. The material density of the downstream layer 128 may begreater than the material density of the upstream layer 126. Thethickness 140 of the downstream layer 128 may be greater than thethickness 138 of the upstream layer 126. In the exemplary embodimentillustrated in FIGS. 2 and 3, the thickness 140 may be about three timesgreater than the thickness 138. The downstream layer 128 may be formedof Libeltex TL4. In other exemplary embodiments, the downstream layer128 may be formed of Libeltex TDL2.

The hydrophobic side 134 may be disposed adjacent the absorbent member124 on an opposite side of the absorbent member 124 from the hydrophilicside 132 of the upstream layer 126. The hydrophobic side 134 may beconfigured to distribute bodily fluids not contained by the absorbentmember 124 to the hydrophilic side 136 of the downstream layer 128. Thehydrophobic side 134 may also be referred to as a wicking side, wickingsurface, distribution surface, distribution side, or fluid distributionsurface. The hydrophobic side 134 may be a smooth distribution surfaceconfigured to move fluid through the downstream layer 128 along a grainof the downstream layer 128, distributing fluid throughout downstreamlayer 128. The hydrophilic side 136 may be configured to acquire excessbodily fluids wicked by the hydrophobic side 134 from the absorbentmember 124. The hydrophilic side 136 may also be referred to as a fluidacquisition surface, fluid acquisition side, hydrophilic acquisitionsurface, or hydrophilic acquisition side. The hydrophilic side 136 maybe a fibrous surface and be configured to draw fluid into the downstreamlayer 128. While illustrated in FIG. 3 as separate components, thehydrophobic side 134 and the hydrophilic side 136 may be opposite sidesof the downstream layer 128 and may be shown as separate components toaid in explanation of the described exemplary embodiments.

As described herein, the upstream layer 126 and the downstream layer 128contain the absorbent member 124, reducing absorbent material lossduring manufacturing, shipping, and use of the pouch 112. Containment ofthe absorbent material prevents loss of the granular absorbentcomponents as the pouch 112 may be moved during the manufacturingprocess. In addition, containment of the absorbent material in the pouch112 formed from the upstream layer 126 and the downstream layer 128 mayreduce loss of the granular absorbent components during use of the pouch112, for example, while placing the pouch 112 adjacent the tissue site106 or positioning the pouch 112 in the therapy system 100. Stillfurther, if the pouch 112 is used at the tissue site 106, containment ofthe absorbent material may limit migration of the granular absorbentcomponents into the tissue site 106.

If the tissue site 106 is small, the pouch 112 may aid the manifold 110in distribution of reduced pressure to the tissue site 106. The upstreamlayer 126 and the downstream layer 128 may enclose the absorbent member124, manifold reduced pressure to the tissue site 106, and wick fluidsfrom the tissue site 106 into the absorbent member 124. The pouch 112may accommodate the increased difficulties of enclosing, manifolding,and wicking that may be experienced when treating a smaller tissue site106. In addition, the pouch 112 may prevent the loss of structuralintegrity associated with using scatter coated absorbent material toform the absorbent member 124 that may often lead to more frequentreplacement of the pouch 112.

During the application of reduced pressure, some pouches containingabsorbent materials tend to become saturated at the point of fluid entryinto the absorbent member itself. If the absorbent material becomessaturated in one area prior to saturation of the absorbent material inother areas, the absorbent material experiences a reduced ability tomove fluid from the point of entry to areas of the absorbent materialthat may be unsaturated. In addition, the amount of reduced pressuredistributed to the tissue site may be reduced, decreasing thetherapeutic benefits of using reduced pressure. If pouches are decreasedin size to be placed adjacent smaller tissue sites or tissue sites thatproduce smaller amounts of exudate, the pouch's absorbent capability maybe further reduced. If the absorbent capability of such pouches isreduced, more frequent dressing changes may be needed, therebyincreasing the cost of supplying reduced-pressure therapy.

As disclosed herein, the therapy system 100 overcomes these shortcomingsand others by providing the pouch 112 as described above with respect toFIGS. 2-3. In the operative exemplary embodiments, the rate of fluidflow received by the pouch 112 may be relatively slow for a relativelylong duration. Placing the hydrophobic side 130 of the upstream layer126 adjacent the manifold 110 may allow the hydrophobic nature of thehydrophobic side 130 to move the fluid along a grain (not shown) of thehydrophobic side 130 across a width of the upstream layer 126. The fluidmovement may be parallel to the manifold 110 and away from the strongestpoint of reduced pressure. This wicking action spreads the fluid drawnfrom the tissue site 106 across a wider area. As the fluid moves throughthe upstream layer 126 from the hydrophobic side 130 toward theabsorbent member 124 it reaches the hydrophilic side 132. Thehydrophilic side 132 draws the fluid into the absorbent member 124. Thegradient of hydrophilicity increases from the hydrophobic side 130 tothe hydrophilic side 132 as the fluid moves downstream toward theabsorbent member 124.

In operation, the increased thickness 140 and increased material densityof the downstream layer 128 aid the distribution of reduced pressure tothe upstream layer 126 and the manifold 110. In one exemplaryembodiment, the upstream layer 126 may have a density of about 80 gsm,and the downstream layer 128 may have a density of about 150 gsm so thatthe relative thickness of the downstream layer 128 to the upstream layer126 may be about 1.875. The relative thickness of the downstream layer128 in other exemplary embodiments may fall in the range from about 1.5to about 3.0 for other reduced-pressure therapy applications. Thedistribution of reduced pressure by the downstream layer 128 aids thewicking action of the hydrophobic side 130 of the upstream layer 126 sothat fluids drawn from the tissue site 106 may be more evenlydistributed in the dressing 102. In turn, more even distribution of thefluids drawn from the tissue site 106 provides for more efficient use ofthe absorbent member 124, increasing the time between replacement of thedressing 102, and decreasing costs as fewer dressings may be needed toabsorb an equivalent amount of fluid.

Positioning of the upstream layer 126 and the downstream layer 128, asdescribed herein, may orient grains of the upstream layer 126 and thedownstream layer 128 in a manner that increases the efficient use of theabsorbent member 124. By placing the hydrophilic side 136 proximate thereduced-pressure source 104. The hydrophilic side 136 may also act as anadditional filter mechanism that may aid in preventing blockage of theprimary filter 121 of the connector 122. The duration during which thedressing 102 can manifold reduced pressure may also extended. By usingmaterials that provide a wicking function, the efficient use ofavailable absorbent materials can be improved.

The use of layers that wick fluids and manifold reduced pressure allowsfor controlled use of the available absorbent material. The layers,arranged as described above, distribute reduced pressure such that fluidmay be more evenly distributed to the absorbent member of the pouch,increasing the total time necessary to saturate the absorbent materialsof the absorbent member as more fluid pathways may be used to distributethe fluid. The use of layers to form the pouch with structures ofdiffering hydrophilicity allows for better control of the fluidsentering the absorbent member of the pouch. The use of layers havingdifferent coatweights allows the properties of the pouch to be matchedto the application in a technically better and cost effective solution.The solution disclosed will result in a greater level of absorptionbefore capacity may be reached without requiring additional absorbentmaterial.

The systems and methods described herein may provide significantadvantages, some of which have already been mentioned. For example, thetherapy system provides improved materials efficiency, lower cost, anddoes a better job at manifolding reduced pressure. The disclosedexemplary embodiment may also be used with inline canisters, forexample, fluid absorbing pouches or fluid absorbing canisters disposedexternal to the dressing.

It should be apparent from the foregoing that an invention havingsignificant advantages has been provided. While shown in only a fewforms, the systems and methods illustrated are susceptible to variouschanges and modifications without departing from the spirit thereof.

Although certain illustrative, non-limiting exemplary embodiments havebeen presented, it should be understood that various changes,substitutions, permutations, and alterations can be made withoutdeparting from the scope the appended claims. It will be appreciatedthat any feature that is described in connection to any one exemplaryembodiment may also be applicable to any other exemplary embodiment.

It will be understood that the benefits and advantages described abovemay relate to one exemplary embodiment or may relate to severalexemplary embodiments. It will further be understood that reference to“an” item refers to one or more of those items.

The steps of the methods described herein may be carried out in anysuitable order, or simultaneously where appropriate.

Where appropriate, features of any of the exemplary embodimentsdescribed above may be combined with features of any of the otherexemplary embodiments described to form further examples havingcomparable or different properties and addressing the same or differentproblems.

It will be understood that the above description of preferred exemplaryembodiments is given by way of example only and that variousmodifications may be made by those skilled in the art. The abovespecification, examples and data provide a complete description of thestructure and use of exemplary embodiments of the invention. Althoughvarious exemplary embodiments of the invention have been described abovewith a certain degree of particularity, or with reference to one or moreindividual exemplary embodiments, those skilled in the art could makenumerous alterations to the disclosed exemplary embodiments withoutdeparting from the scope of the claims.

We claim:
 1. A system for treating a tissue site with reduced pressure,the system comprising: a manifold adapted to be placed adjacent thetissue site; a sealing member adapted to be placed over the tissue siteand the manifold to provide a seal at the tissue site; areduced-pressure source adapted to be fluidly coupled to the manifoldthrough the sealing member; and a pouch adapted to be positioned betweenthe manifold and the sealing member, the pouch comprising: an upstreamlayer having a hydrophilic side and a hydrophobic side, a downstreamlayer having a hydrophilic side and a hydrophobic side, whereinperipheral portions of the upstream layer and the downstream layer areconfigured to be coupled, and an absorbent member enclosed between theupstream layer and the downstream layer, the hydrophilic side of theupstream layer positioned adjacent the absorbent member and thehydrophobic side of the downstream layer positioned adjacent theabsorbent member.
 2. The system of claim 1, wherein the upstream layerhas a first thickness and the downstream layer has a second thickness,and the second thickness is greater than the first thickness.
 3. Thesystem of claim 1, wherein the upstream layer has a first thickness andthe downstream layer has a second thickness, and the second thickness isabout three times greater than the first thickness.
 4. The system ofclaim 1, wherein the upstream layer has a material density of about 80gsm.
 5. The system of claim 1, wherein the downstream layer has amaterial density of about 150 gsm.
 6. The system of claim 1, wherein theupstream layer has a material density of about 80 gsm and the downstreamlayer has a material density of about 150 gsm.
 7. The system of claim 1,wherein: wherein the upstream layer has a first thickness and thedownstream layer has a second thickness; the second thickness is aboutthree times greater than the first thickness; the upstream layer has amaterial density of about 80 gsm; and the downstream layer has amaterial density of about 150 gsm.
 8. An apparatus for collecting fluidfrom a tissue site, the apparatus comprising: an upstream layer having ahydrophilic side and a hydrophobic side; a downstream layer having ahydrophilic side and a hydrophobic side, wherein peripheral portions ofthe upstream layer and the downstream layer are configured to becoupled; and an absorbent member enclosed between the upstream layer andthe downstream layer, the hydrophilic side of the upstream layerpositioned adjacent the absorbent member so that the hydrophobic side ofthe upstream layer forms a portion of an exterior of the apparatus, andthe hydrophobic side of the downstream layer positioned adjacent theabsorbent member so that the hydrophilic side of the downstream layerforms another portion of the exterior of the apparatus.
 9. The apparatusof claim 8, wherein the upstream layer has a first thickness and thedownstream layer has a second thickness, and the second thickness isgreater than the first thickness.
 10. The apparatus of claim 8, whereinthe upstream layer has a first thickness and the downstream layer has asecond thickness, and the second thickness is about three times greaterthan the first thickness.
 11. The apparatus of claim 8, wherein theupstream layer has a material density of about 80 gsm.
 12. The apparatusof claim 8, wherein the downstream layer has a material density of about150 gsm.
 13. The apparatus of claim 8, wherein the upstream layer has amaterial density of about 80 gsm and the downstream layer has a materialdensity of about 150 gsm.
 14. The apparatus of claim 8, wherein: whereinthe upstream layer has a first thickness and the downstream layer has asecond thickness; the second thickness is about three times greater thanthe first thickness; the upstream layer has a material density of about80 gsm; and the downstream layer has a material density of about 150gsm.